Thanks Tornadoken for digging out those quotes.
As ever with events not open to too much public scrutiny at the time and are now around 50 years ago, there are some unresolved matters.
According to a senior manager who I met at Hatfield in the very early 1970s, Boeing were talking to de Havilland (and thought they would eventually be dealing with Airco - the company set up to build the Trident prior to the forced marriages which set up BAC and HS) around the time they were starting work on the initial 727 design in early 1959. These talks were about a similar deal to that between Sud Aviation and Douglas which was initialed at that time and was public knowledge (the final deal was eventually signed in February 1960 and included an agreement for Douglas to build the proposed Caravelle 7).
He went on to state that Boeing thought they were talking about the Medway engined aircraft but when they arrived at Hatfield they were shocked to see how much the BEA changes to the design of the Trident had weakened the saleability - which became apparent to the industry when BEA eventually unveiled its order and spec on August 8 1959.
If that is true, the visit of Dobson and Burke in February 1960 was a futile exercise and the Boeing return visits were probably just to see how the Trident was coming along - perhaps with half an eye on the autoland potential and any other gleanings about what was basically a ground breaking planform.
Whatever else, Boeing's view of the BEA spec confirmed their belief in the Medway engined sized aircraft - a belief that history vindicated.
Whilst the Comet 3 had not sold in the US the Britannia would have had some success but for the problems with the Proteus and the Viscount certainly dented Convair 440 sales, so the Atlantic was not totally unbreachable.